I don't think either of those CPU would hold back a 5850 at stock. The only time you would see a difference in FPS between the two CPUs would be at very high fps (150+) at which point it wouldn't matter. At desired fps (60-100) the difference is very marginal. http://www.tomshardware.com/charts/2009-desktop-cpu-cha...=on&prod=on
As for OCing you should probably be able to get an extra 800Mhz into both chips. The biggest difference would be that the 955 is black edition so its an easier overclock. But as with any chip there's a bit of luck in how high it will OC. Again there won't be a big difference in games.
Hi, please allow the question - why shouldn't AM2+ mobos support 955 ? I'm sorry the question targets wrong direction, the question has to be: Do 955 support AM2+ mobos.
As I know ALL AM3 CPUs are downward compatible to AM/ AM2+ socket and if the mobo has an according BIOS it should work or am I completely wrong?! But there is no compatibility in the other direction! So 955 should support and work fine on such AM/ AM2+ mobos.
The main difference between AM2+/ AM3 CPU is that AM2+ CPUs have only one IMC for DDR2 which is connected to the oputside - may be the other one is on die, too, but not connected to socket pins furthermore AM3 CPUs have two IMCs - for both, DDR2 and DDR3, too, and both are connected to ouside/ socket pins. The only limitation I know is about HT (2000/1600) and energy saving processes (not useable for each single core).
The m/b in question supports ~some~ am3 cpu's. ALL THOSE 95W and under.
What that tells me is that Gigabyte can't guarantee the voltage area/components to handle the higher power draw those cpu's would give and also unfortunately what overclocking will give/need. At least at boot the bios won't give you a unsupported error when it sees the 945, which it probably would with a cpu not on the supported list.
Its a LOWEND m/b